The object of the present finding is a device for controlling the supply of a textile or metal thread to a processing machine, such as a textile machine or a spooling or winding machine, according to the preamble of the main claim. Also forming the object of the finding is a method actuated by one such device.
With particular but non-limiting reference to the textile field, there are many applications in which it is important to precisely measure the tension, quantity and velocity of the thread during the production process. For example, WO2013/045982 on behalf of the same Applicant describes a method for supplying a thread at constant tension and at constant velocity or thread quantity to a textile machine, in which it is necessary to control the constancy of said parameters at a point distant (from zero to tens of meters, for example) from a bobbin from which the thread is unwound. Such text describes the presence of different loops for regulating the tension of the thread and its velocity: in particular it provides that sensors, used for detecting data useful for a second regulation loop (such as the tension of the thread and its supply velocity), placed in proximity to the zone where the thread is drawn from the textile machine for its use, are used for regulating the tension and the velocity of the thread at a point more distant from such machine. In such a manner, the desired quantity/velocity of the thread is obtained in proximity to the textile machine to be supplied thereto.
Also in sewing machines, it is very important for the quality of the process to control both parameters of the thread, i.e. the tension and the quantity of supplied thread. The sewing process almost always occurs through the use of two threads, the first with which the stitch is actually executed and the second that acts as abutment. Generally, in line with how these machines are made, the first thread is physically accessible and thus controllable through a sensor, while the second is not. It is thus essential, through the control of a single thread, to control the quality of the executed stitch by monitoring the tension thereof and the quantity used in order to verify that, during sewing, they remain within a pre-established interval. In particular, through the control of the tension and the quantity of supplied thread, it is possible to intercept with absolute certainty the absence of the second thread.
DE 101 01 747, which forms the base for the pre-characterizing part of claim 1, describes a device for controlling the supply of a thread, which is unwound from a corresponding support, to a processing machine.
The device comprises a body supporting a plurality of rotary members on which the thread is wound and with which velocity detector means cooperate which are connected to a control unit adapted to detect the rotation velocity thereof. Also provided for are means for detecting the tension of the moving thread.